Repainting a plugin's editor


I am trying to build a small plugin host for Mac OS to be used for plugin testing, but have run into problems. I can scan for VST plugins in a directory, create instances, and editors, but I cant get the VST editor to paint correctly. It looks like the editor is painted once, but then it instantly goes all white. Turning a knob, if you can find one, helps and paints the knob correctly for some plugins and in some cases the whole thing is painted. Calling the editor component’s repaint method does nothing.

I get similar problems with the PluginHost example project. Using the git version of juce seems to make the problem less severe and some plugins paint correctly, but not all.

Any clues?